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Re: High ISO impact on PIXEL rendition of colors
In reply to Jarvis393,
7 months ago
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Jarvis393 wrote:
I read a thread on this forum some time ago that questioned why we couldn't just couldn't just substitute high ISO for lighting. http://forums.dpreview.com/forums/post/41152764
I've been thinking about this post lately and I wanted to see if my comprehension of the issue is correct.
As I understand it, pixels convert light into electricity.
The relative amount of light that is captured within each RGB spectrum combines to create a particular color.
ISO amplifies this electrical charge.
At base ISO 100 the light charge is purest.
At ISO 400 the electrical charge is amplified by a factor of 4 times base ISO.
The movie in my head uses an analogy of canned chicken noodle soup.
The soup (color) is strongest right out the can. As more water is added (increased ISO) the soup strength (color) gets diluted and the colors are less vibrant.
Is this how ISO works on color?
A better analogy would be audio tape.
Analog Audio tape has a certain amount of hiss (noise) on it. When your tape is recorded at normal levels, the music drowns out the noise, and you don't hear it (good signal-to-noise ratio)
In a very quiet recording, you might turn up the volume (amplification) to try to boost the signal. However, doing that also boosts that hiss. Now the hiss is noticeable. That's because by amplifying all the audio on the tape, you amplify the hiss (noise) too. The lower the recording level on the tape, the louder the hiss is, proportional to the recording level. (lower signal-to-noise ratio.)
This is almost exactly what happens with digital cameras and high ISO. In good, bright light, the light overwhelms the noise, and you don't see it. As the light hitting the sensor goes down and you boost the ISO to compensate, you amplify the noise as well. Also, there is less signal to work with, so small errors in the recording get amplified too. At very high ISO that can cause your colors and contrast to look really off, in addition to having lots of noise.
--
Regards,
Duncan C
dpreview and PBase supporter.
http://www.pbase.com/duncanc/image/61499136/small.jpg
http://www.pbase.com/duncanc
My macro gallery:
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